1. Technical Field
The present invention relates to a projector, and more particularly to a projector which includes a liquid crystal display panel.
2. Related Art
Currently, a projector having high projection performance and small size is being developed. A typical example of this type of projector including transmission type liquid crystal display panels for red light (R), green light (G), and blue light (B) has been widely used. The liquid crystal display panels included in the projector generate heat when absorbing illumination light. For releasing heat from the liquid crystal display panels, a fan capable of supplying cooling air is employed, for example.
A known cooling structure of a projector supplies cooling air in a direction substantially perpendicular to a plane containing an optical axis along which the liquid crystal display panels are disposed. According this structure, the cooling air can be uniformly supplied to the respective liquid crystal display panels with ease. However, since the fan and a duct through which the cooling air flows are provided above and below the areas where the liquid crystal display panels are disposed, the thickness of the projector is difficult to be reduced. For overcoming this problem, a technology which provides a flow path for guiding the cooling air in a direction substantially parallel with the plane containing the optical axis and sequentially cools the respective liquid crystal display panels and polarization plates has been proposed. For example, JP-A-2001-281613 shows a structure which disposes the liquid crystal display panels around a cross dichroic prism for combining respective color lights, and provides a flow path on each of light entrance surfaces and light exit surfaces of the liquid crystal display panels.
Exit side polarization plates equipped on the light exit surface side of the liquid crystal display panels shield light received from the liquid crystal display panels. In this case, larger amounts of heat are produced from the exit side polarization plates than those from the entrance side polarization plates disposed on the light entrance surface side of the liquid crystal display panels. Thus, cooling air having passed the exit side polarization plates, particularly the G light exit side polarization plate has a higher temperature than the temperature of the cooling air having passed the entrance side polarization plates. The cooling structure proposed in JP-A-2001-281613 has a flow path formed by clearances between the entrance side polarization plates and the liquid crystal display panels and a flow path formed by clearances between the liquid crystal display panels and the exit side polarization plates as separate flow paths. Thus, the cooling air having cooled the G light exit side polarization plate is difficult to sufficiently cool the subsequent exit side polarization plate.